Recently, the cross-axis synchronous flow-through coil planet centrifuge (X-axis CPC) (Ito, Sep. Sci. Tech., 22 (1987) 1971, and 1989) has been remarkably improved with regard to the stationary phase retention, revolution speed, etc. The cross-axis synchronous flow-through coil planet centrifuge has a unique feature among coil planet centrifuges in that the column holder axis is perpendicular to the central axis of the centrifuge (Ito, sep. Sci. Tech., 22 (1987) 1971). In the past, three different models of the X-axis CPC were fabricated and their capability for performing countercurrent chromatography (CCC) was examined using various two-phase solvent systems (Ito, Sep. Sci. Tech., 22 (1987) 1971, and 1989; Ito et al, J. Chromatoqr., 449 (1988) 135 and 153; Zhang et al, J. Chromatoqr., 454 (1988) 185; Ito et al, 455 (1988) 151; Ito et al, J. Chromatoqr., 463 (1989) 305; and Bhatnagar et al, J. Chromatoqr., 463 (1989) 317).
Hydrodynamic studies on retention of the stationary phase in the coiled column of the x-axis CPC indicate that the system provides more reliable retention of the stationary phase for viscous polar solvent systems compared with the high-speed CCC centrifuge based on the type J synchronous planetary motion (Ito, Sep. Sci. Tech., 22 (1987) 1971, and 1989).
Further studies have shown that the phase retaining capacity of the X-axis CPC is enhanced by laterally shifting the position of the column holder along the holder shaft, probably due to the asymmetry of the laterally acting force field between the upper and the lower halves of the rotating coil (Ito et al, J. Chromatoqr., 449 (1988) 135). The degree of the lateral shift of the column holder may be conveniently expressed by L/R where L is the distance from the center of the holder shaft to the coil holder and R the distance from the centrifuge axis to the holder shaft (revolution radius) (FIG. 1). The latest model (Bhatnagar et al, J. Chromatoqr., 463 (1989) 317) with L/R=1 (FIG. 1B) has produced substantially higher stationary phase retention for the polar solvent systems compared with the original model (Ito, Sep. Sci. Tech., 22 (1987) 1971, and 1989) with the central column position (L=0, FIG. 1A).
The present invention involves an improvement over known coil planet centrifuges which allows for separation of macromolecules utilizing aqueous-aqueous two-phase solvent systems.